Angina pectoris which is one of ischemic heart diseases has been known as a disease which often attacks the aged. Although nitric and nitrous acid compounds, calcium antagonists and .beta.-blocker have been used as therapeutic agents therefor, the effect of such a therapeutic agent is far insufficient to treat angina pectoris or to prevent the evolution thereof into myocardial infarction. Recently, the age of a patient with angina pectoris has lowered and the symptom thereof has become complicated owing to change in the style of living, stress increased by the complication of society and so forth, so that a new type of more excellent drug has been desired eagerly.
It is believed that cyclic GMP (hereinafter abbreviated to "cGMP") which is one of cyclic nucleotides and is known as an intracellular second messenger participates in the action of the nitric and nitrous acid compounds among the above drugs which are now used. The relaxing effect of cGMP on the smooth muscle of vessel and bronchus is well known. Although the mechanism of action of these drugs are not always apparent, it is generally presumed that the activity of this cGMP results from the acceleration of the synthesis of cGMP which is caused by the activation of guanylate cyclase. However, the above-mentioned drugs exhibit a low bioavailability and a relatively short time of action. Further, it is reported that the drug resistance is induced, which is a problem in a clinical field.
Under these circumstances, the present inventors have started studies to develop a new type of more excellent drug.
That is, the present inventors have paid their attention to cGMP phosphodiesterase (hereinafter abbreviated to "cGMP-PDE")-inhibiting activity and have made extensive studies on compounds having such an activity for many years. As a result of the studies, they have found that a nitrogenous heterocyclic compound which will be described below has such an activity to be efficacious for various ischemic heart diseases and have accomplished the present invention.
Although quinazoline derivatives useful as drugs are included in, e.g., Publication of International Patent Application by Japanese No. 502462/1990, they are different from the compounds of the present invention in respect of both structure and activity.